Here is the full list of all 43 Over 9000 Zombies! achievements.
Kill 900,000+ Zombies!
Construct 1000 Turrets from random scraps of metal!
Participate in a multiplayer game.
Construct 100 automated turrets.
Kill 90,000+ Zombies!
Kill over 1000 zombie eyes!
Voted the greatest zombie of all time!
The army of the undead will march at daybreak!
The zombie world is independent of our will.
Abused patience turns to fury!
Zombie Napoleon meets his zombie Waterloo!
Health is the greatest gift, a close second is BRAINS!
Terror possessed me then!
If only he had the body of a horse...
A jail is an isolated system.
Blood and Flesh can be trusted.
Decreased Zombotropy.
Quoth the Raven "Nevermore."
Kill over 1000 zombie crows!
No 8th symphony for zombie Sibelius!
Kill over 1000 crabs!
Don't call me slow!
Collect 100 Power Ups!
Your world didn't end!
You didn't donate your organs...
Kill over 1000 zombie dogs!
Kill 9,000+ Zombies!
It didn't taste like chocolate ice cream either...
Not a wimp.
Lots of progress!
Get 30 kills per second!
Get 15,000 damage per second!
You watched the world burn, and survived. It was kind of cool.
Derail the Waltz of the Undead!
Vote for Zombie Thomas Jefferson, or don't.
Get 5,000 damage per second!
Construct a turret from scrap metal!
Kill 1000+ Zombies!
Green IS good.
You won that race.
Get 10 kills per second!
Making some progress...
The first day is always the hardest, except in this case, it's the easiest.